The North American species of Psathyrella.

1972]

PSATHYRELLA

333

KOH, smooth. Hyphae of the subcuticular region heavily incrusted with ochraceous to fulvous amorphous material, septa similarly colored. Clamps present.
Type locality. Huron Mountain Club, Marquette County, Michigan.
Habit and habitat. Gregarious on a drying up pond near the edge.
Distribution. Known only from the type locality.
Observations. This species has the large pleurocystidia of the P. gracilis group
but the spores are slightly shorter, the subcuticular hyphae are more heavily
incrusted, and the stipe is much shorter. It is close to P. orbitarum but the
pleurocystidia are much larger.
Subsection Psathyrellae
Series Tenerae A. H. Smith, ser. nov.
Pileus ad marginem demum pallidus vel subochraceus sed non rubellus;
lamellae non-rubellae. Typus. Psathyrella tenera.
Key to the Species of Series Tenerae
1. Stipe with a pseudorhiza; pleurocystidia 52-70,/ long (see 405. P. nimkeae and
307. P. sumstinii also). 303. P. caudata.
1. Not as above. 2
2. Stipe snow white and unchanging, 1 mm thick; pileus rugose-striate.
304. P. mexicana.
2. Not as above. 3
3. Hyphae of the stipe with pigment incrustations near the septa; gill trama dark
cinnamon-brown in KOH. 305. P. calvinii.
3. Not as above. 4
4. Lamellae vinaceous-buff when young (see 298. P. subdebilis also).
306. P. subincarnata.
4. Not as above. 5
5. Spore apex not truncate or only indistinctly so. 6
5. Spores (at least the larger ones) distinctly truncate. 9
6. Clustered, stipes strigose at the base. 307. P. sumstinei.
6. Not as above. 7
7. Spores in profile with an oblique germ pore. 308. P. tepeitensis.
7. Not as above. 8
8. Lamellae narrow; hyphae of the subcuticular region of pileus dark rusty
brown in KOH. 309. P. uskensis.
8. Lamellae broad, hyphae of subcuticular region pale brownish. 310. P. subolivacea.
9. Most pleurocystidia under 50,/ long (see 235P. arenulina also). 10
9. Many pleurocystidia over 50,u long. 13
10. Pileus cuticle a palisade containing many cystidioid cells as part of the layer.
311. P. brachycystis.
10. Not as above. 11
11. Veil present; pleurocystidia sharply pointed. 312. P. parvicystis.
11. Not as above. 12
12. Brachybasidioles present; stipe 2.5-4 cm long, 1 mm or less thick. 313. P. tenera.
12. Brachybasidioles absent; stipe 5-10 cm long and 0.5-1.5 mm thick.
314. P. intermedia.
13. Growing on sand dunes; spores 9-14 X 6-8 /. 315. P. ammophila.
13. Not as above. 14
14. Stipe 8-12 cm long, 1.5-2.5 mm thick; pileus rugulose. 316. P. alluviana.
14. Not as above. 15
15. Pileus trama hyaline in KOH. 317, P. tahomensis.
15. Pileus trama rusty brown in KOH. 16
16. Cuticle of pileus 2 cells deep; spore wall 0.6,u thick. 318. P. coloradensis.
16. Cuticle of pileus one cell deep; spore wall 1.5,u thick. see 295. P. opacipes.